1/* 2 * Copyright © 2014 Intel Corporation 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining a 5 * copy of this software and associated documentation files (the "Software"), 6 * to deal in the Software without restriction, including without limitation 7 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 8 * and/or sell copies of the Software, and to permit persons to whom the 9 * Software is furnished to do so, subject to the following conditions: 10 * 11 * The above copyright notice and this permission notice (including the next 12 * paragraph) shall be included in all copies or substantial portions of the 13 * Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS 21 * IN THE SOFTWARE. 22 * 23 * Authors: 24 * Jason Ekstrand (jason@jlekstrand.net) 25 * 26 */ 27 28#include "nir.h" 29 30/* 31 * Implements "copy splitting" which is similar to structure splitting only 32 * it works on copy operations rather than the datatypes themselves. The 33 * GLSL language allows you to copy one variable to another an entire 34 * structure (which may contain arrays or other structures) at a time. 35 * Normally, in a language such as C this would be handled by a "structure 36 * splitting" pass that breaks up the structures. Unfortunately for us, 37 * structures used in inputs or outputs can't be split. Therefore, 38 * regardlesss of what we do, we have to be able to copy to/from 39 * structures. 40 * 41 * The primary purpose of structure splitting is to allow you to better 42 * optimize variable access and lower things to registers where you can. 43 * The primary issue here is that, if you lower the copy to a bunch of 44 * loads and stores, you loose a lot of information about the copy 45 * operation that you would like to keep around. To solve this problem, we 46 * have a "copy splitting" pass that, instead of splitting the structures 47 * or lowering the copy into loads and storres, splits the copy operation 48 * into a bunch of copy operations one for each leaf of the structure tree. 49 * If an intermediate array is encountered, it is referenced with a 50 * wildcard reference to indicate that the entire array is to be copied. 51 * 52 * As things become direct, array copies may be able to be losslessly 53 * lowered to having fewer and fewer wildcards. However, until that 54 * happens we want to keep the information about the arrays intact. 55 * 56 * Prior to the copy splitting pass, there are no wildcard references but 57 * there may be incomplete references where the tail of the deref chain is 58 * an array or a structure and not a specific element. After the copy 59 * splitting pass has completed, every variable deref will be a full-length 60 * dereference pointing to a single leaf in the structure type tree with 61 * possibly a few wildcard array dereferences. 62 */ 63 64struct split_var_copies_state { 65 nir_shader *shader; 66 void *dead_ctx; 67 bool progress; 68}; 69 70/* Recursively constructs deref chains to split a copy instruction into 71 * multiple (if needed) copy instructions with full-length deref chains. 72 * External callers of this function should pass the tail and head of the 73 * deref chains found as the source and destination of the copy instruction 74 * into this function. 75 * 76 * \param old_copy The copy instruction we are splitting 77 * \param dest_head The head of the destination deref chain we are building 78 * \param src_head The head of the source deref chain we are building 79 * \param dest_tail The tail of the destination deref chain we are building 80 * \param src_tail The tail of the source deref chain we are building 81 * \param state The current split_var_copies_state object 82 */ 83static void 84split_var_copy_instr(nir_intrinsic_instr *old_copy, 85 nir_deref_var *dest_head, nir_deref_var *src_head, 86 nir_deref *dest_tail, nir_deref *src_tail, 87 struct split_var_copies_state *state) 88{ 89 assert(src_tail->type == dest_tail->type); 90 91 /* Make sure these really are the tails of the deref chains */ 92 assert(dest_tail->child == NULL); 93 assert(src_tail->child == NULL); 94 95 switch (glsl_get_base_type(src_tail->type)) { 96 case GLSL_TYPE_ARRAY: { 97 /* Make a wildcard dereference */ 98 nir_deref_array *deref = nir_deref_array_create(state->dead_ctx); 99 deref->deref.type = glsl_get_array_element(src_tail->type); 100 deref->deref_array_type = nir_deref_array_type_wildcard; 101 102 /* Set the tail of both as the newly created wildcard deref. It is 103 * safe to use the same wildcard in both places because a) we will be 104 * copying it before we put it in an actual instruction and b) 105 * everything that will potentially add another link in the deref 106 * chain will also add the same thing to both chains. 107 */ 108 src_tail->child = &deref->deref; 109 dest_tail->child = &deref->deref; 110 111 split_var_copy_instr(old_copy, dest_head, src_head, 112 dest_tail->child, src_tail->child, state); 113 114 /* Set it back to the way we found it */ 115 src_tail->child = NULL; 116 dest_tail->child = NULL; 117 break; 118 } 119 120 case GLSL_TYPE_STRUCT: 121 /* This is the only part that actually does any interesting 122 * splitting. For array types, we just use wildcards and resolve 123 * them later. For structure types, we need to emit one copy 124 * instruction for every structure element. Because we may have 125 * structs inside structs, we just recurse and let the next level 126 * take care of any additional structures. 127 */ 128 for (unsigned i = 0; i < glsl_get_length(src_tail->type); i++) { 129 nir_deref_struct *deref = nir_deref_struct_create(state->dead_ctx, i); 130 deref->deref.type = glsl_get_struct_field(src_tail->type, i); 131 132 /* Set the tail of both as the newly created structure deref. It 133 * is safe to use the same wildcard in both places because a) we 134 * will be copying it before we put it in an actual instruction 135 * and b) everything that will potentially add another link in the 136 * deref chain will also add the same thing to both chains. 137 */ 138 src_tail->child = &deref->deref; 139 dest_tail->child = &deref->deref; 140 141 split_var_copy_instr(old_copy, dest_head, src_head, 142 dest_tail->child, src_tail->child, state); 143 } 144 /* Set it back to the way we found it */ 145 src_tail->child = NULL; 146 dest_tail->child = NULL; 147 break; 148 149 case GLSL_TYPE_UINT: 150 case GLSL_TYPE_INT: 151 case GLSL_TYPE_FLOAT: 152 case GLSL_TYPE_DOUBLE: 153 case GLSL_TYPE_BOOL: 154 if (glsl_type_is_matrix(src_tail->type)) { 155 nir_deref_array *deref = nir_deref_array_create(state->dead_ctx); 156 deref->deref.type = glsl_get_column_type(src_tail->type); 157 deref->deref_array_type = nir_deref_array_type_wildcard; 158 159 /* Set the tail of both as the newly created wildcard deref. It 160 * is safe to use the same wildcard in both places because a) we 161 * will be copying it before we put it in an actual instruction 162 * and b) everything that will potentially add another link in the 163 * deref chain will also add the same thing to both chains. 164 */ 165 src_tail->child = &deref->deref; 166 dest_tail->child = &deref->deref; 167 168 split_var_copy_instr(old_copy, dest_head, src_head, 169 dest_tail->child, src_tail->child, state); 170 171 /* Set it back to the way we found it */ 172 src_tail->child = NULL; 173 dest_tail->child = NULL; 174 } else { 175 /* At this point, we have fully built our deref chains and can 176 * actually add the new copy instruction. 177 */ 178 nir_intrinsic_instr *new_copy = 179 nir_intrinsic_instr_create(state->shader, nir_intrinsic_copy_var); 180 181 /* We need to make copies because a) this deref chain actually 182 * belongs to the copy instruction and b) the deref chains may 183 * have some of the same links due to the way we constructed them 184 */ 185 new_copy->variables[0] = nir_deref_var_clone(dest_head, new_copy); 186 new_copy->variables[1] = nir_deref_var_clone(src_head, new_copy); 187 188 /* Emit the copy instruction after the old instruction. We'll 189 * remove the old one later. 190 */ 191 nir_instr_insert_after(&old_copy->instr, &new_copy->instr); 192 state->progress = true; 193 } 194 break; 195 196 case GLSL_TYPE_SAMPLER: 197 case GLSL_TYPE_IMAGE: 198 case GLSL_TYPE_ATOMIC_UINT: 199 case GLSL_TYPE_INTERFACE: 200 default: 201 unreachable("Cannot copy these types"); 202 } 203} 204 205static bool 206split_var_copies_block(nir_block *block, struct split_var_copies_state *state) 207{ 208 nir_foreach_instr_safe(instr, block) { 209 if (instr->type != nir_instr_type_intrinsic) 210 continue; 211 212 nir_intrinsic_instr *intrinsic = nir_instr_as_intrinsic(instr); 213 if (intrinsic->intrinsic != nir_intrinsic_copy_var) 214 continue; 215 216 nir_deref_var *dest_head = intrinsic->variables[0]; 217 nir_deref_var *src_head = intrinsic->variables[1]; 218 nir_deref *dest_tail = nir_deref_tail(&dest_head->deref); 219 nir_deref *src_tail = nir_deref_tail(&src_head->deref); 220 221 switch (glsl_get_base_type(src_tail->type)) { 222 case GLSL_TYPE_ARRAY: 223 case GLSL_TYPE_STRUCT: 224 split_var_copy_instr(intrinsic, dest_head, src_head, 225 dest_tail, src_tail, state); 226 nir_instr_remove(&intrinsic->instr); 227 ralloc_steal(state->dead_ctx, instr); 228 break; 229 case GLSL_TYPE_FLOAT: 230 case GLSL_TYPE_DOUBLE: 231 if (glsl_type_is_matrix(src_tail->type)) { 232 split_var_copy_instr(intrinsic, dest_head, src_head, 233 dest_tail, src_tail, state); 234 nir_instr_remove(&intrinsic->instr); 235 ralloc_steal(state->dead_ctx, instr); 236 } 237 break; 238 case GLSL_TYPE_INT: 239 case GLSL_TYPE_UINT: 240 case GLSL_TYPE_BOOL: 241 assert(!glsl_type_is_matrix(src_tail->type)); 242 break; 243 default: 244 unreachable("Invalid type"); 245 break; 246 } 247 } 248 249 return true; 250} 251 252static bool 253split_var_copies_impl(nir_function_impl *impl) 254{ 255 struct split_var_copies_state state; 256 257 state.shader = impl->function->shader; 258 state.dead_ctx = ralloc_context(NULL); 259 state.progress = false; 260 261 nir_foreach_block(block, impl) { 262 split_var_copies_block(block, &state); 263 } 264 265 ralloc_free(state.dead_ctx); 266 267 if (state.progress) { 268 nir_metadata_preserve(impl, nir_metadata_block_index | 269 nir_metadata_dominance); 270 } 271 272 return state.progress; 273} 274 275bool 276nir_split_var_copies(nir_shader *shader) 277{ 278 bool progress = false; 279 280 nir_foreach_function(function, shader) { 281 if (function->impl) 282 progress = split_var_copies_impl(function->impl) || progress; 283 } 284 285 return progress; 286} 287